Biology T3: Infection and Response

What are communicable diseases caused by?

Pathogen themselves or their toxins

What are the 3 main ways diseases can be spread?

• air borne/transfee

• Physical contact

• Water/ food

Direct physical contact?

• any pathogen

• Transmitted via bodily fluids aswell

• Plant deseased commonly caused by this

• Eg.

  • chicken pox

  • HIV

  • Rabies

  • TMV

• a vector can carry these diseases

Air transfer?

• sneezing or coughing transports mucus into air

• Someone else breathes them in getting sick

• Eg.

  • influenza

  • Measles

  • Covid

  • TB

Water transfer?

• Humans ingesting contaminated food or water (raw undercooked food)

• Also plant disease

• Eg.

  • cholera

  • Salmonella

  • Hepatitis

  • Typhoid

How are bacterial diseases spread?

The reproduce rapidly in body, released toxins that make us ill

How do viruses cause disease?

live and reproduce inside humans cells causing damage, rapidly reproducing

How do fungi cause diseases?

produce toxins and can cause growths which damage body

Multicellular organisms, prefer damp/moist environments

How do protists cause disease?

Produce toxins

They have features from plants, animals and fungi

Bacterial disease examples?

• Salmonella:

  • food poisoning from raw/ undercooked food (often chicken)

  • Cause fever, stomach cramping, diahreeh and vomiting

  • Symptoms pass in about a week

  • Hygienic cooking methods can help prevent

• Ghoneria

  • STD

  • Physical contact/ unprotected sex

  • Discharge, pain when urinating

  • Treated with penicillins, some strains have become immune

  • Use safe sex to prevent

Viral disease examples?

• measles

• HIV

• TMR (tobacco mosaic virus)

Measles?

• viral disease

• Air borne, spread through droplets from sneezing or coughing

• Symptoms include red rashes and fever

• Vaccinated as a child

• Can be very serious or even fatal

  • can lead to pneumonia or encephalitis (brain infection)

HIV?

• viral disease

• Physical contact

• spread by sexual contact or other bodily fluids (needles and drugs)

• Symptoms are flu like at first

• Can be symptomless for a few years

• Treated with anti-viral drugs (stops HIV replication)

• Virus attacks immune cells which can cause bad damage and make it difficult to deal with other diseases (eg cancer or infections)

  • called late stage HIV or Aids

TMV/ Tobacco mosaic virus

• viral disease

• Caused mosaic pattern on leaf

• Means plant can’t carry out photosynthesis and is can’t grow well

• E.g on tomato plants

Fungal disease?

• Rose black spots

• Fungus on rose plant

• Causes black or purple spots on leaf, leaves then turn yellow and fall off

• Means less photosynthesis= less growth

• Spread through water or wind

• Treated with fungicides and stripping plant of infected leaves

  • leaves must be destroyed so that they can’t spread disease

Protists disease?

• Malaria

• Part of malarias life happens in mosquitoes (vector for disease)

• Mosquitoes pick up malaria while feeding on infected animals

• Infect organisms by putting protist into blood stream

• Causes repeated fevers and even death

• Can be prevented with insecticides and mosquito nets + stopping mosquitoes feeding

What is a vector?

• a carrier of a disease

• E.g mosquitoes for malaria

Scabs- first line of defence?

• when skin cut platelets in the blood are exposed to air, they then form protein fibres (fibrin) to form mesh over wound

• Platelets and red blood cells get caught in mesh to cause a clot

• Scabs create a layer over the broken skin preventing pathogen from entering

First line of defense- skin?

• skin protects body from physical damage, infection + dehydration

• Outer layer of skin made of dead cells which pathogens cannot penetrate

• Sebaceous gland in skin produce anti microbial oils to kill pathogens

First line of defence- respiratory system

• hair in nose trap larger microbes and dust particles

• The trachea + bronchi have ciliates epithelial- cilia are tiny hair like structures to trap particles

• Goblet cells in epithelium produce mucus to trap dust particles and microbes

• Cilia beat together to waft mucus to back of throat where it is swallows

• Ciliated cells have lots of mitrochondria to provide energy for this

First line of defence- stomach

• stomach produces acid which kills most pathogens

• Hydrochloric acid kills bacteria

How does phagocytosis work?

• phagocyte detects pathogen and moves towards it

• The pathogen is then surrounded and engulfed by the membrane of the phagocyte

• The phagocyte then digests the pathogen with enzymes killing it

How do lymphocytes work?

• different pathogens have different protein markers- called antigens

• Antigens are recognised by lymphocytes that have an antibody to match that antigen

• Antibody bind to the antigen and then weakens it which helps it get killed

• Lymphocytes remember what antibodies are needed for specific antigens (called natural immunity)

What is a vaccine?

A small amount of a dead or harmless or toxins of pathogen that is injected into blood

What is the point of vaccines?

So your body knows how to fight disease if it encounters it for real

Pros and cons of vaccines?

Pro:

• protect from diseases

• Control common diseases

• Prevent epidemics

Cons:

• don’t always work/ don’t give full immunity

• Can have bad side effects

What is herd immunity?

When most people have vaccine so the pagthogen can’t spread, protecting those who do not have the vaccine

MMR virus?

• measles

• Mumps

• Rubella

How many vaccines do you need for MMR?

One at first and then boosters to prevent infection

MMR + autism?

• vaccine may be linked to increased rate of autism

• Delayed side effects of vaccine (not felt/seen right away)

What are painkillers/what do they do?

• stop nerve impulses going to brain, so you feel no or little pain

• Most painkillers based on two natural substances:

  • aspirin (willow bark)

  • Opiates (poppies)

What are antibiotics/ what do they do?

• treat bacterial infections

• Kill bacteria, without killing your own cells

• Made especially to target particular bacteria

What are the two types of antibiotics?

• bacteriacidal: kill bacteria

• Bacteria static: prevents bacteria replication

Why can’t viruses be treated with antibiotics?

• antibiotics designed to treat bacterial infections not viruses

• Bacteria cannot find viruses as they hide in body cells

What is antiviral medication?

• specific for particular viruses

• Don’t kill virus but slow its development

• Difficult to develop antiviral medicines that don’t damage body cells

What is bacteria resistance?

• when new cells develop the DNA is copied to create identical cell

  • this can sometimes go wrong causing mutations

• Mutated bacteria a resistant to the antibiotics ( because the antibiotics don’t recognise it) but cause the same symptom

What are monoclonal antibodies?

• produced from a single clone of cells so are all identical

• They form hybridomas

How do monoclonal antibodies work?

• a mouse is injected with a specific antigen to stimulate the lymphocytes to make the desired antibodies

• The lymphocytes are extracted and combined with a particular tumour cell, detergents are used to break down the cell membrane so the two cells fuse

• This makes a HYBRIDOMA cell which can divide and make more antibodies

• Single HYBRIDOMA cells are clones to produce identical cells that all produce the same antibodies , these are Mabs

• A large amount of Mabs are collected and purified for use

Uses of monoclonal antibodies?

• pregnancy tests - increase in HGC hormone

• Diagnosis- detect cancer cells

• Research - measure levels of substances

• Treatment - bind to specific cells, block receptors and deliver drugs

Advantages of monoclonal antibodies?

• target specif cells, fewer side effects

• Carry drugs for specific parts of the body

• Used in diagnosis

• Produced in large quantities

Disadvantages of monoclonal antibodies?

• expensive and time consuming

• May cause immune response/ allergic reaction

• Not always successful

• Ethical questions about use of animals